So far as is known there has not been developed any form of engine in which the cylinder is driven to revolve. There may be a so-called rotary engine (Wankel engine) in which gas turns a triangular-shaped rotor to rotate a main shaft with respect to a stationary housing. The rotary engine is unlike the present invention engine in which a rod reciprocates against an undulating cam surface to revolve the cylinder itself together with a wheel rotor having a center main shaft. A Wankel engine can be called a Rotary Engine; the present invention engine might be called a Revolving Engine. No form of engine with an automatic compression ratio adjustable undulating saddle-shaped cam employed in the present invention is known to have been previously developed.